The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
An automatic transmission of a vehicle includes multiple clutches to hold gears for selected gear operating ranges. A transmission control module may determine which clutch to disengage (off-going clutch) and which clutch to engage (on-coming clutch) when a change in a gear operation range occurs. A change in a gear operation range may occur according to a shift schedule. Hydraulic pressure is provided to the on-coming clutch to fill a corresponding clutch chamber with transmission fluid and engage a clutch pack. The term “clutch pack” may refer only to friction materials and spacer plates of a clutch assembly. This occurs during a clutch fill mode of transmission clutch control.
During the clutch fill mode, transmission fluid in the clutch chamber is used to push a piston-apply member to engage with the clutch pack. After the piston-apply member is engaged with the clutch pack, hydraulic pressure may further be applied to the on-coming clutch to carry torque during a clutch pressure mode that follows the clutch fill mode. A predetermined hydraulic pressure may be supplied to the clutch chamber during the clutch fill mode.
The clutch fill mode may include supplying the on-coming clutch with hydraulic pressure for a predetermined fill period. The predetermined fill period may be empirically determined. Values, such as clutch volume values, may be stored in a transmission control module and/or memory as part of a look-up table. Predetermined fill periods may be calculated based on flow rate into a clutch under operating conditions. An example of using a predetermined fill period in a clutch fill mode is described in U.S. Pat. No. 4,707,789.